SERIAL I/O
11.3 Clock synchronous serial I/O mode
11.3.2 Transfer data format
LSB first or MSB first can be selected as the transfer data format. Table 11.3.3 lists the relationship
between the transfer data format and writing/reading to and from the UARTi transmit/receive buffer register.
The transfer format select bit (bit 7 at addresses 3416, 3C16, B416) selects the transfer data format. When
this bit is cleared to “0,” the set data is written to the UARTi transmit buffer register as the transmit data,
as it is. Similarly, the data in the UARTi receive buffer register is read out as the receive data, as it is.
(See the upper row in Table 11.3.3.) When this bit is set to “1,” each bit’s position of set data is reversed,
and the resultant data will be written to the UARTi transmit buffer register as the transmit data. Similarly,
each bit’s position of data in the UARTi receive buffer register is reversed, and the resultant data will be
read out as the receive data. (See the lower row in Table 11.3.3.)
Note that only the method of writing/reading to and from the UARTi transmit/receive buffer register is
affected by selection of the transfer data format, and that the transmit/receive operation is unaffected by
it.
Table 11.3.3 Relationship between transfer data format and writing/reading to and from UARTi transmit/
receive buffer register
Transfer format
select bit
Writing to UARTi transmit buffer
register
Reading from UARTi receive
buffer register
Transfer data format
Data bus
UARTi transmit
buffer register
Data bus
UARTi receive
buffer register
DB
DB
DB
DB
DB
DB
DB
DB
7
D
D
D
D
D
D
D
D
7
DB
DB
DB
DB
DB
DB
DB
DB
7
D
D
D
D
D
D
D
D
7
6
5
4
3
6
6
5
4
3
2
1
6
5
4
3
2
1
LSB
(Least Significant Bit)
first
5
4
3
2
1
0
0
2
1
0
0
0
Data bus
UARTi transmit
buffer register
Data bus
UARTi receive
buffer register
DB
DB
DB
DB
DB
DB
DB
DB
7
DB
DB
DB
DB
DB
DB
DB
DB
7
D
D
D
D
D
D
D
D
7
D
D
D
D
D
D
D
D
7
6
5
4
3
2
1
6
5
4
3
2
1
6
5
4
3
2
1
6
5
4
3
2
1
MSB
(Most Significant Bit)
first
1
0
0
0
0
7905 Group User’s Manual Rev.1.0
11-23
RENESAS [ RENESAS TECHNOLOGY CORP ]
